The research being supported by this grant investigates motor and neural aspects of breathing in health and disease. The research is organized into three projects. The first examines the global features of respiratory phase switching in anesthetized cats using a servorespirator driven by respiratory motor outputs. We find that switching occurs in two stages, reversible followed by irreversible. In the second project we seek to identify neurons in the nucleus of the tractus solitarius possibly mediating inspiratory switching. The response to lung inflation tests and to vagal and rostral pontine stimulation are recorded extracellularly. Intra-cellular recordings are being planned. The third project is performed in patients with mechanical abnormalities of the oropharynx appearing during sleep. We are investigating the role of the tensor palatini and the genioglossus muscles in the high resistance syndrome and in periodic airway occlusion during sleep.